II
-aMPf
BRITAIN'S first solaiypowered airr
craft, Solar One, has made its debut
at Lasham Airfield, Hampshire, flying
nearly three-quarters of a mile. Solar
One was powered by electrical energy
gathered by solar cells and stored in
batteries.
The flight, on June 13, was made
by Ken Stewart who reported a take
off speed of 18-20kt, a maximum
speed of about 35kt and a maximum
altitude of about 80ft. Stewart
switched Solar One's electrical power
unit on and off several times during
the flight, before eventually gliding to
the ground as he had used up all the
available runway.
Solar One made a second similar
flight the same day, when pilot Bill
Maidment reached a maximum speed
of 42kt. The aircraft is the brain
child of Freddie To, who formed
Solar-Powered Aircraft Developments*
to produce it. The design of Solar
One has rested largely in the hands
of consultant David Williams. The
group claims to have achieved the
first flight of a solar-powered aircraft
with a short hop last December
(Flight, May 26), but this is con
tested by Larry Mauro of Ultralight
Flying Machines in the US who flew
a converted rigid hang glider in April.
Solar One is an all-new aircraft
and consists of a built-up wooden
framework which is covered by a
heat-shrunk thin plastic material
called Solarfilm—the kind used to
make model aeroplanes. The wing is
in three parts for easy storage and
transport—a centre section and two
outer halves—and features a lami
nated spruce girder box spar. The
fuselage uses a similar internal
arrangement as do the detachable
all-moving fin and tailplane.
The power unit is mounted on a
stalk above the nose of the aircraft
just in front of the pilot. The engine
consists of four permanent magnet
electrical motors, joined together by
a chain drive to produce a nominal
output of 4 h.p. The drive in
corporates a 3:1 reduction to the
fixed-pitch propeller which ends up
being driven at about 1,100 r.p.m.,
but at present this gradually drops
off as the batteries become exhausted.
Solar One's "battery" consists of
24 Nickel/Cadmium accumulator
cells joined in series and having a
capacity of 25Ahr. When these are
fully charged they provide enough
power for the aircraft to climb for
about eight minutes, though they
supply useful energy for several
more minutes.
Solar powered aircraft develop
ment's has invested about £16,000 in
developing Solar One. This includes
roughly £8,000 for materials, £6,000
of which was spent on the 750 solar
cells fitted to the aircraft. The cells
are thus the most expensive item on
the aircraft, which partly accounts for
why more have not been fitted to
date. Solar One is designed to have
almost all its top wing surface covered
by cells—those fitted at present weigh
less than 101b, including wiring—.it
is claimed that this would give the
craft a sustained rate of climb of
70ft/min in bright sunshine.
Control of Solar One is fairly con
ventional with power operated by an
on/off switch. The team is currently
looking at ways to improve Solar
One's performance and plans to make
a cross-country flight soon. One of the
aims of the group is to develop their
solar-powered aircraft for sport and
recreational flying.
*Solar-Powered Aircraft Developments, 5A Lyndhurst
Gardens, London NW3.
SOLAR ONE DATA
Length 22ft; Span 68ft; Wing area 260ft2;
Empty weight 2301b; Aerofoil section Wort-
man FX180, 18 per cent thickness/chord; Power
unit 4x Bosch 1 h.p. electric motors; Propeller
wooden, 5ft 3in diameter; Solar cells 7S0x3in
diameter and 0-008in thick; Batteries 24 Nickel/
Cadmium cells, capacity 25Ahr.
Top Solar One takes-off on a flight of nearly three-quarters of a mile. Below left The 750 solar cells are attached to the inboard rear portion of the
wings. The cells are covered by a transparent film to reduce drag. Below right The team responsible for Solar One, from left to right, Rill Maidment,
Ken Stewart, Freddie To and David Williams